Regulation of Cell Proliferation and Apoptosis by ERK Signaling Pathway in Air way Smooth Muscle Cells of Rats

The regulative role of extracellular signal-regulated kinase (ERK) signaling pathway on proliferation and apoptosis in rats′ airway smooth muscle cells (ASMCs) was investigated. Primary cultures of ASMCs were established and cells between passages 4 and 7 were used for experiments. ASMCs were treated with ERK activator epidermal growth factor (EGF) and inhibitor PD98059. The expressions of ERK mRNA and protein were detected by RT-PCR and immunofluorescence staining. Proliferation of ASMCs were detected by MTT colorimetric assay and 3Hthymidine incorporation. Apoptosis of ASMCs were detected by Hoechst staining and Annexin-V FITC PI double staining. The levels of ERK1/2, phosphorylated forms of ERK1/2(p-ERK1/2) and procaspase-3 protein were detected by Western blotting. The expressions of ERK mRNA and ERK protein were obviously observed in ASMCs. Compared with control, the absorbance (A_ 490 ) value and DNA synthesis index of PD-treated ASMCs were significantly decreased (P0.05). The apoptotic index and the percentage of the early apoptotic cells were significantly increased (P0.05). The expressions of ERK1/2 and pERK1/2 protein were significantly down-regulated. The expressions of procaspase-3 protein was significantly increased. Compared with control, the A_ 490 value and DNA synthesis index were significantly increased (P0.05) in EGF-treated cells. Apoptotic index and the percentage of the early apoptotic cells were significantly decreased (P0.05). The levels of ERK1/2 and pERK1/2 protein were significantly increased, and the levels of procaspase-3 protein were significantly decreased. There were no significant differences between control and P+E group(P0.05). ERK signaling pathway may play an important role in regulating ASMCs proliferation and apoptosis and ERK regulating the apoptosis of ASMCs possibly relates to the expressions of procaspase-3 protein. The finding will help to understand the mechanisms of asthmatic ASMCs involved in abnormal proliferation.